Agree that we are always talking about FOV regardless of focal length of lens. I think the industry had no choice but to talk about 35mm equivalent because there is nothing else to compare with that makes sense. So the focal length of a 800 mm lens on a 1.6 cropped sensor has a focal length of 1280mm ("35mm equivalent").
Cropping does not change the focal length. Maximum FOV is the same as 1280mm on a FF. I don't see why anyone needs to actually call the lens' focal length anything different than what is written on it. Whether I use my 6D or my Pentax Q on my 400mm or 600mm lenses, they are still 400mm and 600mm. I know what 400mm means on all 3 sensor sizes that I use with my 400mm lenses.
I see it like this; you have a lens with certain properties; you put a sensor behind it to capture a rectangle of a certain size in its projection. Within that sensor, you have a certain pixel density (and microlenses, and a possible AA filter) to resolve it. The lens is what it is, and the sensor is a tool to capture part of its projection. Capturing a smaller rectangle does not increase focal length, does not increase "reach", and does not increase captured subject detail; higher pixel density, however, does do the latter.
Two photographers standing next to each other are both shooting the same subject with the same 500mm lens; one with a D30 and one with a 5D3. The person with the D30 brags that he is shooting with more reach, with more magnification, and at a greater effective focal length. All three, however, are pure nonsense, and given the same technique, the person with the 5D3 will be getting better detail of the subject, with 1.65x the linear resolution, and 2.75x as many pixels on the subject.
Focal length has nothing to do with sensor size or density, or whether or not you crop in software. Focal length describes how far behind the front element a subject at infinity is in focus; period.
It is possible that it has the same noise levels per unit of sensor area. Having the same noise at the full image level would almost be science fiction come true.
"Reach" is another hollow term, IMO. I do not use it (except when discussing it as a concept). What percentage of a frame a subject fills isn't even significant in regards only to the viewfinder, because not all viewfinders have the same AOV. What good would it do if your subject was half as high as the viewfinder frame, but the AOV was a narrow tunnel? The word "reach" implies a change of perspective. True reach would be a lens that was 100 feet long and you placed the front element in front of the subject, 105 feet away. Otherwise, you are not "reaching", but magnifying, or just cropping.
You did not say if it was from the same distance, or if it was the the same filling of the full frame from different distances. Getting the same composition with the full-frame is impossible with the same optics, because the perspective will be different. From the same distance, the camera with the smaller pixels will get more detail, but if the 7D2 does not improve on read noise compared to the 7D, then there will be more subject-level noise at high ISOs (but less at base ISO to about 500, 250 with HTP).
The increase in f-stop with a TC is irrelevant as far as potential SQ (subject quality) is concerned. The subject gives less absolute exposure (light per unit of sensor area), but it cancels that out by having the subject cover more sensor area, so the loss of subject photons is minimal, and only a small amount due to small t-stop factors in the converter. What the TC does do, however, is make AF more difficult or impossible, as f-stop directly rules the day with phase-detect AF. Going to a higher ISO to use a TC at the same shutter speed can actually decrease noise, especially in a Canon DSLR at low ISOs, where an ISO 100 subject without a TC will have more read noise with normalized subject size, as would ISO 400 and a 2x TC. At higher ISOs, you don't have the gains in subject noise levels, but you still have finer Bayer CFA artifacts, and finer "pixel crud" in general; all images whether from a 7D with a strong AA filter, or a Sigma SD9 with its virtual point sampling, all look defective in one way or another at 100% pixel view on a coarse monitor. The more camera pixels you have of your subject, the better, as downsampling overcomes the camera's pixel crud, and leaves only the coarse monitor's display flaws.